Queensland residents are braced for floods to rise today as meteorologists confirmed that 2010 was one of Australia's wettest on record.

Water levels in the largest affected community, Rockhampton, are expected to peak today with the swollen Fitzroy river predicted to reach its second-highest level on record. Residents in flooded towns have worked desperately to build sandbag levees in the hope of holding back the rising waters. In Rockhampton, a rise of 20cm would inundate 400 more homes and lap at the front doors of another 4,000.

"Let's hope we dodge the bullet. Every centimetre counts," said the Queensland state disaster co-ordinator, Ian Stewart.

The floodwaters are expected to begin to subside after today, although it could be a month before they dry up completely.

Australia's weather bureau said the La Niña weather pattern which caused the floods was expected to last another three months. It also said that last year was Australia's third wettest on record.

La Niña produces monsoon rains over the western Pacific and south-east Asia. More than a week of rains has flooded an area the size of France and Germany, cutting off 22 towns and affecting 200,000 people.

The rains have forced 75% of coal mines to close in Queensland, the world's biggest exporter of coal used in steel-making. The state's premier, Anna Bligh, said the floods had had "a massive impact on the international markets and the international manufacture of steel".

Australia accounts for more than half of global coking coal exports, which are vital to steel-makers, especially in Asian countries such as China. Queensland's mines produced 35% of Australia's estimated 259m tonnes of coal exports in 2009. It is expected to take months for some mines to return to normal production.

Wheat production in Australia, the world's fourth-largest exporter, has also been affected. The flooding in Queensland, along with heavy rains and earlier flooding across eastern Australia, could mean up to half the national crop, about 10m tonnes, becomes animal feed or low-grade milling grains.

"Queensland is a very big state. It relies on the lifelines of its transport system, and those transport systems in some cases are facing catastrophic damage," Bligh saidre.

"Without doubt this disaster is without precedent in its size and its scale here in Queensland. What I'm seeing in every community I visit is heartbreak, devastation."